To compare documents in Word, go to Review, Compare, Compare, choose the version you sent as the original document and the one sent back to you as the revised document, and click OK. Word creates a third document with all the differences marked, including the ones nobody marked with Track Changes, and leaves the two files untouched.
How to compare two Word documents, step by step
Word's comparison is on the Review tab, in the Compare group, and it creates a new document with the differences.
- Open the two documents you want to compare: the one you sent and the one you have been sent back.
- On the Review tab, in the Compare group, click Compare and, in the menu that opens, Compare again, the option for two versions of the same document.
- Under Original document, choose the version you sent. If it is not in the list, browse for it on your computer.
- Under Revised document, choose the version you have received.
- Click More to check what is compared and how it is shown (we look at this in the next section).
- Click OK. If either version contains tracked changes, Word warns you; with Yes, it treats those revisions as accepted and carries on with the comparison.
The result is a third document. In it, any revisions your version had are treated as accepted, and everything that is different in the other side's version appears as a marked change, just as if it had been written with Track Changes turned on. The two starting files stay as they were. Microsoft documents this comparison for Word for Microsoft 365, Word 2024 and Word 2021 on Windows.
Two details decide whether the comparison is useful to you. The first is what you choose as the original: always compare with the exact version you sent, not with your internal draft, or your own later tweaks will get mixed into the result. The second is that the comparison does not depend on the other side's Track Changes: Word checks the content of the two files against each other, so changes nobody marked also show up.
Which comparison options are worth checking
The options under the More button decide what counts as a change, in how much detail it is marked and in which document it appears.
Microsoft's help explains that you can choose what Word takes into account when comparing, for example comments, formatting and text changes. Word's technical documentation lists ten types of difference that the comparison can mark or ignore: formatting, case changes, white space (paragraphs and spaces), tables, headers and footers, footnotes and endnotes, text boxes, fields, comments and moves.
- What to compare. In a contract or a brief, leave tables, footnotes, headers and footers ticked: they are text too and they can change too. You can untick formatting if you are only interested in the content, especially when one of the versions comes from a PDF.
- Show changes: character level or word level. At word level, Word marks the whole word even if only one letter has changed; at character level, only what changed. The first reads better in long texts; the second spots a different figure in an amount, a date or a deadline straight away.
- Show changes in: new document, original document or revised document. By default, Word puts the result in a new document. If you choose the original or the revised one, Word writes the marks into that file and changes it. To keep the version you were sent exactly as it arrived, stick with the new document.
How to see the differences: the display options
Word shows the result as revision marks, and lets you choose whether to see the two starting documents alongside it.
Besides character or word level and the destination document, which you choose before comparing, there are two ways of looking at the two versions:
- With or without the source documents. In Review, Compare, Show Source Documents you decide whether to see the two starting files next to the result, only the original, only the revised one or neither. For the compared document, Microsoft describes a screen in three parts: the list of revisions on the left, the document with the changes in the middle and, on the right, the original and the revised document. If that is too much information, Hide Source Documents leaves only the document, with vertical red lines in the margin where there are changes.
- Side by side, without marks. If you would rather read both versions at once, open both and click View, View Side by Side, in the Window group. With Synchronous Scrolling, the two move together. It is useful for rereading, but it marks nothing: you have to find the differences yourself.
The marks in the compared document are revisions like those of Track Changes: you go through them with Next and Previous, and accept or reject each one from the Review tab. How to work with them, how to change the way the marks are displayed and how to send the document back with your own changes marked is explained in Track Changes in Word.
After comparing, it is time to reply: a comment on each change you don't accept or an email to the other side. If you don't dictate much, Word's Dictate button may be enough; we explain it in how to dictate in Word. With ablalo you dictate it with a shortcut in Word, in your email or in any program, and the text appears where the cursor is, including inside a comment. In the legal register it applies the Libro de estilo de la Justicia (the RAE and CGPJ style guide for the Spanish justice system), whose most frequent mistakes in legal documents we have summarised, and your voice is transcribed on your own computer.
Compare, Combine or View Side by Side: which to use
Compare is for two versions of the same text; Combine is for bringing together in one document the revisions of several people.
| Compare | Combine | View Side by Side | |
|---|---|---|---|
| What for | See what changed between your version and the one sent back to you | Bring together what several reviewers have changed | Read two versions at once |
| Where | Review, Compare, Compare | Review, Compare, Combine | View, View Side by Side |
| Result | New document with the differences as revisions | Document that brings together the original and the copy, with the changes marked | Two windows, one next to the other |
| Marks the differences | Yes | Yes | No |
Microsoft warns about this in its help: if the changes come from several reviewers, don't use Compare, use Combine. Combine works with two documents at a time: you combine the first copy with the original, save the result and combine the next copy with it, and so on with each one. In the Label unmarked changes with box you type a name, for example the other side's or a colleague's, so you know who proposed the changes that arrived unmarked.
How to compare a Word document with a PDF
To compare with a PDF, first open it in Word, which creates an editable copy and leaves the PDF intact.
- In Word, go to File, Open and choose the PDF (with Browse if you need to look for it in a folder).
- Word warns you that it is going to make a copy and convert its content; the original PDF does not change. Click OK.
- Save that copy as a Word document.
- Compare: your Word version as the original document and the converted copy as the revised document.
The result depends on the conversion, and Microsoft points out its limits. It works better with PDFs that are mostly text; a book chapter or a document that looks like it came off the photocopier will not convert with good formatting. Also, the copy may not match the PDF page for page: lines and pages may break at different points. So that these layout differences don't fill the result with marks, untick formatting in the comparison options and, if breaks and spaces that are not real changes keep showing up, white space too. Microsoft documents opening PDFs in Word for Microsoft 365 and in Word 2024, 2021, 2019 and 2016.
A practical use: when the final version arrives as a PDF, ready to sign, compare it with your last Word file. It is the quick way to check that the text matches what was negotiated.
In Word for the web, on a Mac, online and with AI
Word for the web does not compare documents; Word for Mac does, with almost the same steps as on Windows.
Word for the web
Microsoft says in its help that, for now, the web version of Word does not let you compare documents. The way out it suggests is to open the file in the desktop app from the ribbon itself, with Editing, Open in Desktop App, which requires having Word installed. With Microsoft's tools, then, comparing is a job for desktop Word.
Word for Mac
In Word for Mac, comparison is under Review, Compare, Compare Documents, and combining under Review, Compare, Combine Documents. You choose the original and the revised document just as on Windows, and the comparison settings open with the arrow at the bottom of the dialog box. The result is a new copy based on the original, with the differences as revision marks; the original copy is not changed.
Online comparison tools and AI assistants
When you upload or paste the two versions into a comparison website or an AI assistant, your client's document goes to a third party's service. With a template letter that doesn't matter; with a contract or a brief containing personal data, it does. Before doing it, you should know who processes the document, where, how long they keep it and whether they use it to train their models: these are the questions we go over in client confidentiality and GDPR when using AI in a law firm.
There is also a difference of method. Word's comparison marks every difference according to the options you chose; an AI assistant's answer is a summary written by it. If you use one, treat it as a second reading, not as a substitute for the marks.
What Word's comparison doesn't solve
Word's comparison tells you what has changed, not whether the change matters: that is still the lawyer's job.
- It doesn't work on the web. You need desktop Word, on Windows or Mac.
- With a PDF, it depends on the conversion. If the PDF is not mostly text, the Word copy may not be faithful, and then the marks pick up the conversion as well as the changes.
- It doesn't tell you what the other side marked. If their version arrives with tracked changes, Word treats those revisions as accepted for the comparison. If you want to know what they changed without marking it, first read their revisions as they arrive and compare afterwards: whatever shows up in the comparison and was not among them is what they didn't mark.
- It compares two versions, not a chain. With several copies from different reviewers, use Combine, two at a time.
- It doesn't judge anything. A moved comma and a rewritten clause appear the same way, as revisions. Deciding which ones you accept is still up to you.
In short
To compare documents in Word, use Review, Compare, Compare in desktop Word: the version you sent as the original, the one sent back to you as the revised document and the result in a new document, with all the differences marked as revisions even if the other side didn't use Track Changes. For several reviewers, Combine; for a PDF, open it in Word first and untick formatting. Word for the web doesn't compare, and the websites or AI assistants that do receive your client's document.
Sources: Microsoft, Compare document differences using the legal blackline option, Combine document revisions, Merge two documents (Windows, Mac and web), Compare and merge two versions of a document (Mac), View and compare documents side by side, Edit a PDF and Track changes in Word; Word technical documentation, CompareDocuments method and source documents in the comparison. Checked on 22 October 2026.
Frequently asked questions
How do you compare two Word documents to see the differences?
In desktop Word, go to Review, Compare, Compare. Choose the earlier version as the original document and the new one as the revised document, and click OK: Word creates a third document with the differences marked as revisions and does not change the two files.
What is comparing documents in Word for?
To find out what has changed between two versions of the same text without reading them side by side, for example the contract you sent and the one the other side sends back. Changes made without Track Changes show up too, because Word checks the content of the two files against each other.
What two display options are there when comparing documents in Word?
Under Show changes you choose between character level, which marks only what changed, and word level, which marks the whole word. Under Show changes in you decide whether the result goes to a new document, which is the default, to the original or to the revised one.
Can you compare Word documents online for free?
Not with Word for the web: Microsoft says the web version does not compare documents and points you to the desktop app. There are third-party websites that compare texts, but to use them you upload the document to their service, something worth weighing up before doing it with a client's document.
Can you compare a Word document with a PDF?
Yes, in two steps: open the PDF in Word with File, Open, which creates an editable copy, save it and compare it with your document. Microsoft warns that the conversion works better with PDFs that are mostly text and that lines and pages may not match the original.
Can you compare Word documents with AI?
You can ask an AI assistant to do it, but you give it the content of both documents and its answer is a summary, not a mark for each change. With client documents, first check what that service does with what you upload, as we explain in client confidentiality and GDPR when using AI.